Abstract: Strengthening intellectual property protection is an important part of improving the property right system, which is of great significance to stimulate the innovation of private enterprises. Taking the national intellectual property demonstration city policy implemented in 2012 as a quasi natural experiment, this paper selects the data of A-share private listed companies in Shanghai and Shenzhen from 2005 to 2020 as the research sample, and uses the multi-stage double difference model to investigate the impact of intellectual property strategy on the innovation of private enterprises. The results show that intellectual property strategy will significantly promote the innovation of private enterprises, which is still valid after a series of robustness tests. The heterogeneity test shows that intellectual property strategy plays a more obvious role in promoting the innovation of private enterprises in central and western regions, high financing constraints and high-tech industries. The mechanism test shows that the intellectual property strategy mainly acts on the innovation of private enterprises through government subsidies and improving talent agglomeration. Therefore, we should continue to strengthen the protection of intellectual property rights, continuously optimize the business environment and encourage private enterprises to research and innovate.

Key words: intellectual property strategy, innovation, private enterprises, quasi natural experiment, heterogeneity